Beta-nodaviruses are single-stranded RNA, non-enveloped virions and are the etiological agents of Viral Nervous Necrosis (VNN) or fish encephalitis, a disease characterized by the development of a vacuolating encephalopathy and retinopathy, and the presence of virus-like particles in neurons of infected fish. VNN represents a significant barrier to commercial aquaculture activities because of the frequency of incidence of the disease, the high levels of mortality (approaching 100%) and its widespread distribution across warmwater and coldwater farmed fish species.
Chemical disinfection to destroy nodavirus in isolated bodies of water based on chlorine, iodine or ammonium is the standard preventative method, but a vaccine would be preferred due to concerns about the effects of such chemicals on the marine environment. At present there is no commercially available vaccine for protecting fish against nodavirus infections, and specifically against VNN. It is an object of the present invention to provide a vaccine which confers commercially significant protection on farmed fish against nodavirus infection.